Roof construction in a low-pitched roof generally consists of a roof deck, an insulation barrier above the deck, a weather resistant layer applied to the insulation layer, and optionally a layer of heat resistant material. The roof deck generally includes materials such as wood, gypsum, concrete, steel, and the like. Above the roof deck, insulation boards are typically applied to provide thermal insulation and a uniform surface to which the weather protective layer is applied.
There are generally two types of roofing situations, one is a new roof construction and the other is where an existing roof is being reroofed, which typically occurs when the existing roof is leaking. Insulation boards employed in reroof situations are generally referred to as recovery boards. Recovery boards can also be made with a variety of core materials that are typically coated with a protective facer that can be either rigid or flexible and can be fire or flame-retardant. In a reroofing operation, the roof deck can refer to the existing roof, including the existing insulation and weather resistant layer.
Recovery boards are generally applied to an existing roof deck assembly to provide a uniform surface when recovering an existing roof. The existing roof is typically hot and wet, and the environmental conditions in which the reroof takes place is typically hot, humid, and wet. The most common recovery boards are made of woodfiber or extruded polystyrene. The woodfiber is typically coated with a thin layer of asphaltic material on one side, and those recovery boards that are made of polystyrene typically do not contain a facer. While insulation boards are typically not affected by environmental conditions during the construction of a new roof, the hot and damp conditions encountered during reroof situations can warp the facers of many recovery boards.
To seal the roof from the elements, recovery boards are typically covered with various materials including molten asphalt, modified bitumen membrane, rubberized asphalt, or an elastomeric composition such as EPDM (ethylenepropylene diene monomer). Not all sealing materials, however, are compatible with each type of recovery board. For example, molten asphalt can not be used with extruded polystyrene. Correct combinations of sealing material and recovery board are known to those skilled in the art. The heat resistant layer of material, which is generally applied directly to the weather resistant layer, can include gravel, river stone, foam or a layer of mastic followed by granules.
Application of the weather protective layer can be accomplished by a number of means, usually dictated by the type of material employed. For example, sheets of a protective membrane can be rolled out over the roof and bonded together by torching or the use of an adhesive.
Although inexpensive and generally in wide use, woodfiber and polystyrene-containing insulation or recovery boards are often ineffective in hot, humid and wet environments. Particularly, woodfiber boards will disintegrate in a wet, humid environment, which is common in a reroof operation. Polystyrene will expand, bow, or distort in similar environments, especially when exposed to the extreme heat experienced upon roofs in warmer climates.
The patent literature does include panels and boards used for roofing operations. Built-up roof constructions and the components thereof, for example, are well-known in the art as generally explained in Blanpied, U.S. Pat. No. 5,001,005, Dybsky et al., U.S. Pat. No. 4,944,818, and Rosato et al., U.S. Pat. No. 4,388,366. With regard to insulation boards, Blanpied teaches a rigid foam board comprising a thermosetting plastic foam sandwiched between two facers; the facer comprising glass fibers, non-glass filler, and non-asphaltic binder. Likewise, Dybsky et al. teaches a composite roofing substrate panel comprising a core of combustible material such as fibers or foams and a facer of noncombustible material such as glass fibers coated with a bituminous material. Rosato et al. teaches a laminate insulation board comprising a plastic foam core and at least one facer sheet forming both a protective layer and a venting means for fluids; the facer sheet comprising fine glass fibers bonded together with polyvinyl acetate.
All existing polyisocyanurate boards, or iso boards as they are sometimes known, employ facers on the two parallel sides with the largest surface areas. A facer usually consists of a composite with paper, fiberglass and various binders and additives. The standard facer is an approximate composition of 80 percent by weight recycled paper, 15 percent by weight fiberglass and 5 percent by weight additives and binders. These fiberglass facers actually contain minimal fiberglass as a reinforcement for the facer or sheet material. The high paper content of this facer yields a facer that readily absorbs water, which is not desirable in a polyisocyanurate insulation board. These standard facers typically absorb as much as 60 percent by weight water per ASTM C209. Additionally, these standard facers are very permeable to gases such as oxygen subsequent to foaming of the polyisocyanurate, which diminishes the insulative or R-value properties of the iso board. For example, it has been shown that many hundred and perhaps thousands of cubic centimeters per hundred square inches of oxygen can permeate a standard facer within 24 hours per ASTM D3985.
Thus, a need exists for an iso board which is stable throughout the manufacturing process and more moisture resistant. The use of a composite which contains isocyanurate and/or urethane foam between facers that comprise a polymer, such as polyamide 6,6, optionally reinforced with glass strands or glass fibers and optionally a filler material, such as calcium carbonate, clay, mica and the like, and optionally various dyes or colorants, makes the iso board of the present invention dimensionally stable, relatively insensitive to moisture in reroofing and, reduced air permeability which improves the R-value.